Rendering



Oct. 10,1933.. H. o. HALvoRsQN 1=:r AL 1,930,169

RENDERING Filed Aug. 29. 1950 rhum M f Patented oct. 1o, 1933 1,30,l59

lalvor Orin Halvorson, Ramsey County, and Ed ward M. Schmitz and RobertC. Murray, Austin, Minn., assgnors to Geo. A. Hormel & Company, Austin,Minn., a corporation of Delaware Application August 29, 1930. serial No.v473,612

15 Claims. (01.87-13) a This invention relates to the rendering of fats,ample in the rendering of hog fatfor producas for the making of lard.tion of lard, it is desired to extract from the The invention has forits general objects the natural tissue as much of the fat as possible,provision of a method whereby fats may be ren-` and to avoid so far aspossible the deleterious 5 dered from natural tissue with increasedrapideiects on the fat such as may result from its 60 ity and withminimum deleterious eiect from partial decomposition or breaking down,or oxithe rendering heat and accompanying inuences. dation or othermodications of the retaining A particular object is the provision ofsuch tissues, under the action of the heat or other method whereby amass of fat-containing tissue inuences present during the rendering.'I'he 'may be heated quickly and uniformly to a temlatter is ofparticular importance where the fat 65 perature eiective to render outthe fat, withis to be used as a constituent of or in the prepaoutinvolving the excessive heating of the mass ration of foods, as thepresence of free fatty in parts and the consequent deleterious eiectsacids or other decomposition products from the on the fat. fat ortheretaining tissue adversely affects the Yet another object is theprovision of such keeping quality of the product and results in 70method whereby fats may be effectively sterilrancidity and otherundesirable modiications in ized incident to rendering at temperaturesmaits taste and color. It is recognized that proterially below that ofboiling water and without longed heating and excessive heating of thefatprolonged subjection of the fat to the heat. containing tissue areproductive of these dele- A Yet another object'is the provision of suchterious and undesirable effects. For example, 75 method whereby a highpercentage recovery of the best neutral lard is obtained by treating fatfrom natural tissues may be accomplished small batches at comparativelylow temperatures. rapidly and economically. Such procedure, however, isnecessarily costly,

Yet another object is the provision of such particularly as regards. theproportion of time method particularly qualied to obtain the adrequiredto the quantity of product, and this 80 vantages above mentioned in therendering of results from the length of time required to heat hog fatfor production of lard. a batch under the necessary limitations of theYet another object is the provision of such applied temperature. methodwhereby the rendering may be carried The present invention provides amethod on either as a continuous procedure or as a batch whereby theuniform heating of the entire'mass 85 treatment. of fat-containingtissue may be effected very Other and further objects will be pointedout rapidly without any of the mass being subjected or indicatedhereinafter or will be apparent to to temperatures productive ofdeleterious eects. one skilled in the art upon an understanding ofDescribed generally, the method of the present A the invention or itsemployment in practice. invention contemplates a preliminary treatment90 In the drawing forming a part of this sp'eciiicaof the fat-containingtissue in such fashion as tion we show, and hereinafter describe,certain to form a fairly homogeneous mass having an examples ofprocedure and apparatus which will appreciably higher electricalconductivity than serve to explain the practice of the invention, thefat-containing tissue -before such prepara- 40 but it is to beunderstood that these are presented tion, and then subjecting the massto the pas- 95 for purpose of illustration merely and are not sageofelectrical current at such density as to to be construed inany fashioncalculated to limit generate throughout the mass a. temperature theappended claims short of the true and most sufciently high to. renderout the fat. Incident comprehensive scope of the invention in the art.to such heating the mass may be subjected to The illustrations in thedrawing are all schepressure for the purpose of augmenting its con- 100j matic in nature, ductivity to the current and increasing the sepa-Fig. 1 representing a sectional elevation of an ration of the liquid fatfrom the retaining tissue. apparatus Which maybe utilized fOr Practice0f The application of the current to the mass should the method as abatch procedure; be sumciently distributed to obtain an approxi- Fig. 2a longitudinal sectional elevation of apmately uniform currentdensitythroughout the 105 paratus in which the method may be practicedmass.

as a continuous procedure; and The invention will be understood in moredetail Fig. 3 a cross-sectional detail on substantially' from anexplanation of certain examples, which line-3 3 of Fig. 2. will be madeby reference to the accompanying In the rendering o! fats by heat, asfor exdrawing. For the production of lard, for ex- 11o ample, thesuitable hog fat is .cut up, as in a chopper of conventional sort, intocomparatively small pieces, as of the order of one-half inch orone-quarter inch cubes, andwith it is thoroughly mixed a small portionof ordinary salt, for example one-tenth of one per cent to onefourth ofone per cent by weight. 'Ihis mixing of the salt with 'the fat may beaccomplished quite rapidly and quite thoroughly by the chopper. Forbatch procedure, a suitable quantity of the fat as thus prepared ispacked with approximately uniform ldensity in a rendering receptacle,such as the receptacle designated 10 in Fig. 1, which receptacle iseither constructed of a'material which is electrically non-conductive,or has an electrically non-conductive lining as indicated at 11. Thereceptacle has an electrically conductive perforate bottom 12 upon whichthe charge of fat is supported, and a draining bottom 14 for receivingthe discharge from the perforate bottom. A pressing plunger 15 isarranged to-operate in the receptacle 10 so as to apply pressureuniformly over the entire top of the contained charge or mass offat-containing tissue, which latter is indicated generally at 16. Thispressing plunger presents on its lower surface, for contact with themass 16, an electrode 17, suitably electrically'insulated from theoperating parts. The electrodes 12 and 17 are connected across asuitable source of high frequency alternating current, such as the motorgenerator 18. The electrodes '12 and 17 being in contact with theopposite surfaces of the mass 16, the application of a suitablepotential to said electrodes at a proper alternating high frequency willpass a high frequency current through the mass 16. This current willgenerate heat in the mass, the temperature obtained in a given timebeing dependent on the current density. Although the fat-containingtissue in its natural condition might constitute a very poor conductor,the modication-by comminuting it and/or addition of salt as abovedescribed reduces its resistance to a comparatively low value and givesit a high thermal emciency under a current of the sort described. As aconsequence, heat is generated in it rapidly by the passage of the highfrequency current, and the distribution of heat is practically uniformthroughout the mass The frequencies which are eifective are thosesubstantially higher than the ones used generally on service lines, yetlower than radio frequencies. Although frequencies ranging from 240 to2500 cycles per second are 'feasible under various conditions, thedistinctly effective range of frequenci'es is between about 500 and 2000cycles per second, and within this range the frequencies above 1000cycles per second are most effective. Highly important results areobtained by the use of these high frequencies. The passage of currentbetween the electrode and the mass is effected without corrosion, orburning or searing effects, and a substantially uniform distributionofthe current and thermal e'ects throughout the mass is obtained.Consequently, the mass is heated up throughout at a uniform rate, andthe rendering out of the fat from the tissue in the center of the massbegins approximately as soon extraction of the rendered fat, and suchpressure serves also to expedite the separation of the rendered rat fromthe tissue and the mass.' 'rne rendered fat drains through the perforatebottom 12 into the draining bottom 14, whence it is conducted to filtersor other apparatus for such further-treatment as may be desired. Thetemperaturel generated in the mass may be denitely controlled byappropriate regulation oi.' the applied voltage, so that the maximumtemperature to which the mass is subjected may be held to any desiredlimit. Thus the temperature to which the mass is subjected may bechanged at different stages in the procedure, a selected temperaturebeing employed for the first part of the rendering, and a highertemperature thereafter being applied. The fat removed under the highertemperature may be kepty separate from that taken off under the lowertemperature. The pressure may be applied to the point of expressing fromthe tissue almost all of the fat.

Highly important results are obtained from th rapid and uniform heatingof the mass. None of the fat or the fat-containing tissue is subjectedto an undesirably high temperature, nor is any of the fat orfat-containing tissue subjected to the heat for an unduly long time. Asa consequence, the possibility of hydrolyzation of the fat is minimized,as is also the possibility of oxidation dehydration or other undesirablemodification of the fat-containing tissue. 'I'hese factors result incertain highly desirable characteristics of the product. For example,the free fatty acid content of the product is limited to a very smallquantum, as is particularly apparent in the comparison of lard renderedby this process with lard obtained by steam rendering of similarfat-containing tissue. Lard rendered by the present process is also freefrom much of the color which is ordinarily found in unrened steamrendered lard. Even without treatment with fullers. earth, lard renderedby this process is much Whiter than steam rendered lard which has beentreated with fullers earth in the usual manner. The -ilavorcharacteristics of lard rendered by this method are particularlydesirable as it is approximately neutral or devoid of taste. The saltused in the preliminary treatment of the fat-contain ing tissue does notgo out with the fat in the rendering, but remains in the water held bythe residual tissue. Because of the rapid and uniform heating of themass in the rendering, it is not necessary to employ such hightemperatures or hold the mass under heat for a time such as to result inany appreciable evaporation of water from the tissue. The water thusremaining in -the tissue retains the salt and limits to a large extentthe capacity of the residual tissue for reabsorbing the melted fat.Consequently, itis possible to extract from the tissue, by the presentmethod, a higher proportion of the fat than is feasible in methods inwhich higher temperatures v or more prolonged heating are involved.

It appears that the action of the high frequency ciu'rent in the mass iseffective to reduce very materially the opportunity for 'enzymatic andother decomposing action. The action of the high frequency currentappears to lower the resistivity of enzymes and organisms to heat, sothat their action may be stopped at temperatures which are reached veryearly in the heating of the mass by the high frequency current.

In Figs. 2 and 3 is illustrated schematicallya type of apparatus inwhich the method may be carried on as a continuous procedure. In theseillustrations the reference numeral 20 designates a feeder casing inwhich operates a screw con- 150 tained by forming the renderingreceptacle with decreasing cross-sectional area as illustrated. )et

its termination, the rendering receptacle communicates with a dischargereceptacle 28 in which 'is a screw conveyor 29 operable to dischargematerial from the rendering receptacle. The conveyor 29 is operablecontinuously from a suitable The rendering receptacle 24 may be made ofelectrically non-conductive material, or it may be lined withnon-conductive material as indicated at 31, and within it, suitablyinsulated from each other and from the casing', are electrodes 32suitably disposed for extensive surface contact with the mass ofmaterial contained in the rendering receptacle. 'I'hese electrodespreferably are disposed at uniform spacing from each other, and they areconnected across a source of suitable high frequency voltage, such asthe motor generator 34.

In use of this apparatus for practice of the method, the fat-containingtissue, after being suitably prepared by subdivision into small piecesand/or otherwise treated to give it the desired electrical conductivity,as by addition of salt, is deposited in the hopper 25, and by operationof the conveyor 21 is fed continuously into and through the renderingreceptacle 24. In the rendering receptacle it is subjected vtocompression, by the continued operation of the conveyor` and theresistance offered to its movement by the rendering receptacle, soY thatit is formed into a compact composite mass. By the action of theconveyor 21 this 'mass is moved' progressively through the renderingreceptacle, encountering the electrodes 32 as it proceeds, and beingsubjected to increasing compression which serves to maintain the mass inclose contact with the electrodes. During its movement between thevelectrodes, there is passed through the mass of material a highfrequency current which has the effect of generating heat as abovedescribed. The

fat which is rendered out of the tissue runs downwardly through themoving mass of material and into the sump, whence it is dischargedthrough the perfor'ate portions 26. In this movement the heated fatpasses through the material which is below the electrodes, and serves toheat the material not yet subject to the heat-generating current.

Upon reaching the terminus of the rendering yreceptacle 24, the residuetissue, from which the greater proportion of the originally containedfat has by that time been rendered out, is dischargedinto the dischargereceptacle 28, through l as a press element for obtaining the finalextrac- To accomplish this, the discharge receptacle and conveyor 29 maybe constructed as press members with which the adjustable press cone 35cooperates to increase,

compression of the material in the receptacle 28, the liquids expressedbeing discharged to the collector 36 and the residual tissue beingdischarged vas tailings at the chute 37. To aid in the extraction of thefat in the press, the receptacle 28 may be suitably heated.

It will be apparent that with the use of this.

method the handling of theimaterial and extraction of the fat may becarried on as a continuous procedure, quite rapidly, with all of theadvanltion ofthe fat from the residue materialin the dischargereceptacle.

tages above described, and that a very vhigh percentage of the fatcontained in the material may be recovered in the course of theprocedure.

We claim:

l. A process forrendering fat from fat-containf an electric current indensity sufiicient to generate in the tissue subjected thereto heat of atemperature adequate to render fat out of said tissue and permitting therendered fat to drain awayfrom the tissue during the heating thereof.

2. A method of rendering fat from fat-containing material whichcomprises treating the material to render it conductive to a highfrequency electric current and then applying electrodes to a mass'of thematerial and passing through the mass a high frequency electric currentin sumcient density to generate throughout the mass of materialsubjected to said current density a temperature adequate to render out'fat contained in said material. v

3. A process as specified in claim 2 and'wherein the current-producingvoltage is applied immediately to extensive surface areas of the mass.

4. A process as specified in claim 2 and wherein the frequency of thecurrent is of the order of 1000 to 2500 cycles per second.

5. A process as specii'led in claim 1 and including the'subjection ofthe mass of material to compression during the passing of the currenttherethrough.

6. A process as specified in claim 2 and including subjecting the massof material to compression during the passage of the currenttherethrough.

'7. A process of rendering fat from fat-containing material whichcomprises subdivi'ding the material into pieces, mixing salt with thematerial, and passing through a mass of the material thus prepared anelectric current at high frequency in sufficient density to' generatethroughout the mass subjected thereto a rendering heat, thecurrent-producing voltage being applied to the mass over an extensivesurface area thereof.

8. A process as specified in claim '7 and wherein the current passedthrough the material is of a frequency approximating 1500 cycles persecond.

9. A process as specified in claim 'l and including subjecting theA massof material to compression during the passing of the currenttherethrough.

10. A process of rendering fat from fat-con- .taining material whichcomprises treating the material to render it conductive to highfrequency electrical current, feeding the material progressively 4in acontinuous stream, passing through the stream in the course of itstravel a high frequency electric current 4in density sumcient togenerate a rendering heat in the material subjected thereto, andpermitting the rendered fat to drain from the portions of the streamthrough which the current is passing.

1l. A process as specified in claim 10 and wherein the material in thestream is subjected to compression in the course of its progress andduring the passage of the current through it.

12. A process as specified in claim 1 and wherein material in the streamis subjected to contact with the heated rendered fat for purpose of heatexchange, before it is subjected to the electric current. l

13. A method for rendering constituents from organic material whichcomprises treating the material to increase its electrical conductivity,passing high frequency electric current through a mass of the materialand permitting the rendered constituents tor drain out of the mass Whilethe current is passing therethrough.

14. A process lfor rendering fat from fat-containing tissue whichcomprises treating the tissue to render it readily conductive toelectrical current, passing the treated tissue in a stream between andin contact with electrodes of opposite polarity, passing through theportion of the stream between the electrodes an electric current indensity sumcient to generate in said tissue heat of a temperatureadequate to render fat out of the same, and draining rendered fat out ofsaid portion of the stream While the current is passing therethrough.' f

15. A method of rendering fat from fat-containing' tissue whichcomprises treating the tissue to render it conductive to electriccurrent, passing the material as a stream between and in contact withelectrodes. passing through the portion of the stream between theelectrodes an electric current in density suicient to generate thereinheat effective to melt the fat, and draining the melted fat from saidportion of the stream into a portion of `the stream approaching theelectrodes.

HALVOR QRIN HALVORSON. EDWARD M. SCHMITZ. ROBERT C. Y.

